Atomic and Nuclear PhysicsDOE-HDBK-1019/1-93MODES OF RADIOACTIVE DECAYRev. 0Page 27NP-01DecayChainsWhen an unstable nucleus decays, the resulting daughter nucleus is not necessarily stable. Thenucleus resulting from the decay of a parent is often itself unstable, and will undergo an additionaldecay. This is especially common among the larger nuclides. It is possible to trace the steps of an unstable atom as it goes through multiple decays trying toachieve stability. The list of the original unstable nuclide, the nuclides that are involved asintermediate steps in the decay, and the final stable nuclide is known as the decay chain. Onecommon method for stating the decay chain is to state each of the nuclides involved in the standardX format. Arrows are used between nuclides to indicate where decays occur, with the type of decayAZindicated above the arrow and the half-life below the arrow. The half-life for decay will bediscussed in the next chapter. Example:Write the decay chains for rubidium-91 and actinium-215. Continue the chains until a stablenuclide or a nuclide with a half-life greater than 1 x 10 years is reached.6Solution:PredictingTypeofDecayRadioactive nuclides tend to decay in a way that results in a daughter nuclide that lies closer to theline of stability. Due to this, it is possible to predict the type of decay that a nuclide will undergobased on its location relative to the line of stability on the Chart of the Nuclides.Figure 9 illustrates the type of decay nuclides in different regions of the chart will typically undergo.Nuclides that are below and to the right of the line of stability will usually undergo decay.-Nuclides that are above and to the left of the line of stability will usually undergo either decay or+electron capture. Most nuclides that will undergo decay are found in the upper right hand regionof the chart. These are general rules that have many exceptions, especially in the region of the heavynuclides.